The present invention relates to stepper motor controllers for controlling one or more stepper motors and a method for controlling a stepper motor with plurality of field coils. More specifically, the present invention relates to stepper motor controllers and methods that require a group of individual drivers and a common driver. Each of the field coils is connected between one of the individual drivers and the common driver.
Stepper motors have an armature that provides a rotor and one or more field coils that form a stator. Stepper motor controllers for such stepper motors supply driver currents to the stepper motor field coils in selected sequences to incrementally rotate the armature in steps. The driver current sequences can be selected to control a stepper motor to rotate the armature by full steps, partial steps, micro steps and by maintaining constant driver currents the armature can be maintained in a desired fixed angular position.
Stepper motor controllers have drivers for providing the driver currents. These drivers are typically two series connected complementary power transistors coupled between power supply nodes. When one driver is connected one end of a field coil and another driver is connected to the other end of the field coil a configuration known as an H-bridge is formed and therefore current can flow in either direction though the field coil.
Often stepper motor controllers are formed as a single semiconductor package or may be only part of the circuitry of a large multi-function semiconductor package. The trends and demands in the electronics industry require semiconductor packages to have relatively high functionalities condensed on small areas of silicon real estate. The overall size of the semiconductor package is also required to be as small as possible and therefore the number of external terminals (pins or pads or balls) is usually limited. It would therefore be desirable if the number of power transistors, and external terminals, associated with the stepper motor drivers were reduced without affecting the stepper motor controller's resolution requirements of incrementally rotating the armature in full step, partial step or in some circumstances even micro step increments.